I don’t think there is a way to achieve what you are looking to do with a running container. What you would more than likely need to do in order to save your couchbase data is to commit your current container to a new image and then do a docker run specifying the new port range and the new image name.
Also, just in case you weren’t aware of it, you can persist your data between container restarts (or even between deleting and spinning up new containers) by using a mounted volume. With a mounted volume, you end up storing your couchbase data in a directory on your host computer and then mount that folder into the container at runtime. This way your db data will always be available to your containers no matter how many times you update them/throw them away.